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United States Patent | 6,218,822 |
MacQuigg | April 17, 2001 |
An apparatus and method for performing curvature trim in a voltage reference circuit that allows a curvature error to be trimmed after the circuit has been packaged. The curvature trim may be performed by switching in segments of one or more non-linear resistors, such as n-type lightly doped drain (LDD) diffused resistors, having a curvature characteristic that is opposite to the normal band-gap curvature. Specifically, a network of non-linear resistors may be selected via selection bits stored in a non-volatile memory. Since various combinations of the resistors may be selected by programming the memory, the curvature of a band-gap reference can be adjusted after final packaging. This curvature correction method achieves a reliable and accurate correction for the curvature variations associated with various process changes.
Inventors: | MacQuigg; David R. (Tuscon, AZ) |
Assignee: | National Semiconductor Corporation (Santa Clara, CA) |
Appl. No.: | 416897 |
Filed: | October 13, 1999 |
Current U.S. Class: | 323/313; 323/316; 323/907 |
Intern'l Class: | G05F 003/16; G05F 003/20 |
Field of Search: | 323/313,314,315,316,907 |
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